Serial bcd adder

ABSTRACT

A digital processing system wherein a binary-coded decimal full adder forms along with a display shift register a loop-like circuit for circulating information signals. The system provides a series synchronism system which reduces the number of circuit elements.

United States Patent Nomiya et a1.

[ May 28, 1974 SERIAL BCD ADDER 3,214,576 10 1965 Propster, Jr. 235 170 x 3,249,745 5/1966 Burkhart 235/165 X 175] Inventors: Nomyai Taka" Tsulk" both 3,571,582 3 1971 Kelling 235/170 of Tokyo, Japan 3,584,206 6/1971 Evans 235/170 3,621,219 11/1971 Washizaka 235/170 [73] Asslgnee Tokyo Japan 3,707,622 12/1972 Hataro 235 176 [22] Filed: Dec. 21, 1972 [21] Appl. No.: 317,303 P rimary Examiner-Malcolm A. Morrison Assistant Examiner-David H. Malzahn [30] Foreign Application Priority Data Attorney, Agent, or Firm-Cra1g and Antonelli Dec 24, 1971 Japan 46-104579 52 us. c1 235/176, 235/170 1571 ABSTRACT [51] Int. Cl. G061 7/50 di gital processing system whereln a binary-coded [58] Flew of Search 235/176 decimal fulladder forms along with a display shift register a loop-like circuit for circulating infonnation signals. The system provides a series synchronism system [56] References Cted which reduces the number of circuit elements.

UNITED STATES PATENTS 2,872,107 3/1959 Burkhardt 235/170 9 Claims, 18 Drawing Figures MOST SIGNIFI- 1N CANT DIGIT 5L6 51111 7 REGISTER V115 ,s,[ gRu'reoRe Rxb i Rx Rxcl I T i BINARY 1 v, i E i 1 i JSIGNIFiCANT 1 58 R I l I I X ILFSDI DIGIT D11- b FA1 1,011,. A

= 3212a 1116 9 MEMORY CIRCUIT 31 1 EB E D|G|T REGISTER ADDER minimums m4 3.813Q623 xnEEI 2 0F 5 Cpz lllllllllllllllllllllllllllllllllllllll Cpl IIHHIIHIIIIIIIHHIIIIIIITIIIII||||| Bil J'l Fl ['1 ['1 F] H n I"! H PEG. 2%

0p IIIFIIIIIIIIIIIIIIIII I WP I I PAIIENIEIIIIII 2 I914 3.813523 SHEET k (If 5 REGISTER .Wfiso MSD LSD FIG. 5a 'II III IIII I Fg LSD MSD I LSD FIG. 5b 'II IIIIIIII I B s MSD LSD FIG. 50 I I I I I IIII'I R LSDMSD LSD FIG. 5d 'I I II I I I I I I I I R}xb fRxo FIG. 5e IIIIIIIIII I I Rxb REGISTER RXO FIG. @0 I I fi I I I l I I I I T LSD Msb IRXO LSD FIG. ah I I II I II'II I I I Rxb Rxa ILSDMSD I LSD FIG. 66 IIIIIIIII I I PATENTEDHAYZBIQM 3313523 SHEET 50F 5 REGISTER \RXDJLSD M59 LSD FIG. 70 ll lllllllllil FiG.7b I IIIIIIH E.*c ll llllllllm IG. II ll lllllllll 5 PRIOR ART FLIo 'NPUT REGISTER I L 1 ADDER REGISTER J J/FLso \RYO O REGISTER \Rzo FLzo , 1 SERIAL BCD ADDER The present invention relates to a digital processing system which employs shift registers connected in ser1es.

A principal object of the present invention is to provide a processing system wherein the number of circuit elements is reduced, and more particularly, a digital processing system which is suitable for a small-sized calculator such as a desk-top calculator.

Another object of the present invention is to provide a digital processing system which can easily display processed information signals.

Still another object of the present invention is to provide a digital processing system which can easily execute arithmetics such as multiplication and division.

Yet another object of the present invention is to provide a digital processing system which can shorten the length of the register. means.

A further object of the present invention is to provide a digital processing system which is free from overflow of a processed result.

According to the present invention, there is provided a digital processing system characterized by a first display shift register-of a certain capacity prescribed for numerical information for display in a display unit (for example, a capacity for storing numerical information of eight digits), a calculating shift register having the same capacity as said first display shift register, a binary digit full adder connected to the output side of said first display shift register and having a memory circuit (delay circuit) with a capacity of two to four bits, and a second display shift register disposed between said binary digit full adder and said first display shift register and having a capacity which is equal to one obtained by subtracting the capacity of said memory circuit of said binary digit full adder from the capacity of said first display shift register; said first display shift register, said second display shift register and said full adder forming a circulative closed circuit for information signals; the total capacity bit time of said first display shift register, said second display shift register and said delay circuit in said full adder is time-shared by a sector pulse corresponding to the capacity bit time of said calculating shift register; thus the information signals of the two series-connected display shift registers are subjected .to calculating processing.

These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein FIG. 1 is a block diagram showing an embodiment of a digital processing system according to the present invention;

FIGS. 2a and 2b are wave-form diagrams of controlling and synchronizing pulses which are used in the digital processing system of the present invention;

FIGS. 3 and 4- are block diagrams each showing a delay type full adder which is employed in the present invention;

FIGS. 5a 5e, 6a 6c and 7a 7d are explanatory diagrams for illustrating changes of information signals of display shift registers in the digital processing system of the present invention; and

FIG. 8 is a block diagram showing an example of a prior-art digital processing system.

Referring to FIG. 1, R designates the first display shift register which has a fixed capacity. In the illustrated embodiment, the capacity of the shift register R is eight digits (32 bits) from the least significant digit LSD, to the most significant digit MSD R indicates the second display shift register which is directly coupled to the register R at a stage preceding thereto. The capacity of the register R is set so that the total capacity (32 bits) of the capacity (for example, four bits) of a binary digit full adder AD referred to below and the capacity (forexample, 28 bits) of the register R itself may be equal to the capacity (32 bits) of the first display shift register R R represents a calculating shift register, which has the same capacity (32 bits) as the first display shift register R Shown at AD is the binary digit full adder, to which are supplied the output of the display register R for the posterior stage and the output of the calculating register R or a different control'input Dt The output of the binarycoded decimal full adder AD is supplied through a line F L2 to the input side of the display register R); for the anterior stage. The binary-coded decimal full adder AD is composed of a binary full adder FA a memory circuit DM for carry detection (for BCD correction) and a binary full adder FA The carry detecting memory circuit DM has, for example, N digits (at least two bits). The number of digits of the memory capacity of the display register Rxb for the anterior stage is subtracted to the amount of the length of the N digits. Letting N2, N and N, be the numbers of digits of the anterior stage display register R posterior-stage display register R and calculating register Ry, respectively, they are thus set so as to hold the relation of N N, N N Accordingly, among the three registers, the length of the anterior-stage display register R is shorter by the N digits than that of the other register R or R while the sum between the length of the carry detecting memory circuit DM and that of the anterior-stage display register R becomes equal to the length .of the other register R or R The above-noted relation may also be defined in the manner the memory capacity of the circuit DM is 4N bits, the memory capacities of the first display shift register R and the calculating shift register R are both 4N bits and the memory capacity of the second display shift register is 4(N N bits, where N, and N are integers of at least one and N N,. An indicator unit IN for indicating the information contents of the display register R (the first and second display registers R and Rxb) is also provided. information subjected to calculating processing are read out from the output side of the first display shift register R to the indicator unit by a line FL and are brought into visible display or recording display by the indicator unit. A decoder circuit and a drive circuit which are connected between the display shift register R and the indicator unit IN, are omitted for the sake of convenience of explanation. In the case where the display system of the indicating unit is a dynamic one, it is desireable in order to make the display efficiency high (in order to raise the duty ratio) that the information signal to-be-indicated is also read out from the output side of the second display shift register R by a line F1 In this case, it is possible to increase the application repetition period of the information signal to the indicating unit, thereby lengthening the lighting (light emitting) time of the indicator unit. It is required, however, that either the information stored at the last digit LSD of the shift register R X or the last digit LSD of the shift register Rx is always in the blank state so as to prevent the information from both registers being mixed and displayed. In other words, the foregoing construction is very effective in a processing system in which the information stored in the circulating path including the registers R and R and the memory circuit DM amounts to eight digits being a half of the total capacity, and in which the remaining eight digits are brought into the blank state after completion of the calculation. The transfer of information from the display shift register R to the calculating shift register Ry is accomplished by a line F L. Although a controlling gate portion necessary for the calculating processing is incorporated into each of the lines which is controlled on-and-off by a synchronizing pulse for control, the controlling gate section is omitted from the drawing.

The information signal stored in the calculating register R ,-the display register R and the memory circuit DM of the full adder AD is shifted by clock pulses Cp and Cp as shown in FIG. 2a. The total capacity bit time (64-bit time) of the loop-like closed circuit passing through the display register R and the full adder AD is prescribed at double of the capacity bit time (32-bit time) of the calculating register Ry. The information of the first display register R X and the second display register R are distinguished by timing pulses (pulses for distinguishing higher digits and lower digits) Sp shown in FIG. 2b, and are subjected to the calculating processing. The timing pulse Sp has a pulse width equal to the period of the digit pulse Dt shown in FIG. 2a, and is synchronized with the digit pulse DT,. At this time, the information of the first display shift register R is processed for a period of time T in which the timing pulse Sp is of a high level, while the information of the second display shift register R M is processed for a period of time T in which it is of a low level. For example, in case of subjecting the information of R and that of Ry to addition processing, the information of R and Ry are applied to the adder Ad in the period of time T of the timing pulse Sp.

With reference to FIGS. 2a and 2b, description will now be made of various pulse signals used in the embodiment and in a desk calculator etc., to which the embodiment is applied. In the figures, the upper level of a pulse signal indicates a reference potential or the ground potential (logic l while the lower level represents a negative potential (logic 0"). The clock pulses Cp, and Cp are generated by, e.g., astable multivibrators, and tick away the time by themselves in the calculator. They are used for the drive or shift of, e.g., memory elements (delay type flip-flop circuits) connected in cascade within the shift registers R R and Ry and the memory circuit DM for correcting a binarycoded decimal number. The respective output signals of the memory elements are transmitted to those at the succeeding stages by the timing of the clock pulses Cp Bit signals Bt, Bt, are used in case of, e.g., converting binary parallel signals derived from the encoder into binary series signals. In the embodiment, the judging signal of the bit signal Bt, is utilized in the binary-coded decimal full adder as stated below. Digit signals Dt Dt are used as, e.g., digit changing signals in the dynamic display system. In the embodiment, they are used in order to add 1 to or subtract the same from the second operand in multiplication and division as is stored in the shift register for display. The sector pulses Sp have the state changed to T or T every eight digits, and can be composed from the digit signal Dt or Dt by utilizing a flip-flop circuit and a logical gate circuit. Digit pulses Dp distinguish the digits of a binary-coded decimal number. Word pulses Wp are used for distinguishing words or instructions. The characteristic equations of the respective pulses Dp and W are re resented by D Btf CE and W,, Dt Cp S; which can be composed of the foregoing pulses. The bit signals Bt, BL, and the digit signals Dt Dt can be respectively generated from the clock pulses Cp and the bit signal Bt, by making use of, e.g., counters. Herein, the pulse width of the bit signals Bt Bt, corresponds to the period of the clock pulses Cp, or CM, and to the time of 1 bit of the series binary signal. The pulse width of the digit signals Dt, Dt and the period of the digit pulses Dp correspond to the period of the bit signals Bt Btq, namely, the time of one digit (four bits) of the series binary-coded decimal number. The period of the word pulses Wp corresponds to double of the period of the digit signals Dt Dt The delay type full adder AD is constructed as shown, by way of example, in FIG. 3. Referring to the figure, DL, represents a delay circuit having a memory capacity of four bits (one digit), DL and DL;, delay circuits for effecting delay of one-bit time, CC a correction judging circuit, G a gate circuit which has its gate opened by a predetermined timing signal Bt,, and CG a generator for generating in response to an output of the correction judging circuit CC an output which serves to add 6 in decimal number (01 10 in binary number) to the binary full adder FA The delay circuits DL DL correction judging cirucit CC, generator CG and gate circuit G constitute the carry detecting memory circuit DM.

With such a construction, in the case where the result of addition in the binary full adder FA, is 0 9," the output of the binary full adder FA is supplied through the delay circuit DL, to the binary full adder FA in consequence of the addition of the outputs of the posterior-stage register X and the register Y as have been supplied to the binary full adder FA,. The output of the binary full adder F a is transmitted to the anterior-stage register X or R In the case where a carry arises in consequence of the addition in the binary full adder FA a binary carry signal is supplied through the delay circuit DLg to the input side of the binary full adder FA to add l to a higher binary digit. At this time, it is a matter of course that, even with the binary carry, no overflow occurs beyond four binary digits. The correction judging circuit CC and the gate circuit G do not operate.

In the case where the result of the addition in the binary full adder FA, is 10-15, the binary carry signal is supplied through the delay circuit DL to the input side of the binary full adder PA, for the binary carry in the binary full adder FA In addition, the correction judging circuit CC is operated by an instruction of the delay circuit DL,. The correction judging circuit CC supplies an output to the generator CG, and simultaneously supplies a decimal carry signal to the binary full adder FA to conduct decimal carry. The output of the delay circuit DL, and that of the generator CG are added by the binary full adder. FA The binary carry is conducted in such way that the output of the binary full adder FA is supplied through the gate circuit G, adapted to be opened by the predetermined timing signal E, to the input side of the binary full adder FA with delay of one-bit time by the delay circuit DL In this manner, -5 in the binary-coded decimal notation is transmitted from the binary digit full adder AD, that is, the binary full adder FA Further, in the case where the result of the addition in the binary full adder FA, is 16-19, the output of the binary full adder FA is supplied through the delay circuit DL to the input side of the binary full adder FA thereby to conduct the binary carry and the decimal carry. The instructing output of the delay circuit DL is not supplied to the correction judging circit CC. Instead, the instructing output of the binary full adder FA, operates the correction judging circuit CC. The output of the correction judging circuit CC operates the generator CG. The output of the generator CG is supplied to the input side of the binary full adder FA On the other hand, the output of the binary full adder FA is supplied through the delay circuit DL to the input side of the binary full. adder FA The binary carry signal is supplied through the gate circuit G and delay circuit DL from the output side of the binary full adder FA Since the decimal carry has been already conducted in the binary full adder FA no decimal-carry is executed in the binary full adder FA In this manner, an output of 6-9 is transmitted as the output of the binary digit full adder AD, that is, the output of the binary full adder FA FIG. 4 shows another embodiment of the binarycoded decimal full adder in FIG. 1. In FIG. 4, the same parts or parts having the same functions as in FIG. 3 are assigned with the same symbols. The delay circuits DL DL the correction judging circuit CC and the generator CG constitute the carry detecting memory circuit. A point of difference from the embodiment in FIG. 3 resides in that, without using the gate circuit G, the output of the binary full adder FA is supplied through the delay circuit DL to the correction judging circuit CC and the input side of the binary full adder FA With such a construction, in the case where the result of addition in the binary full adder FA, is 09 or 16-19, the foregoing applies,

In the case where the result of the addition in the binary full adder FA, is 10-15, the output of the binary full adder FA, is supplied through the delay circuit DL to the input side of the binary full adder FA,, thereby to conduct binary carry. The output of the binary full adder FA is supplied through the delay circuit DL to the binary full adder FA On the other hand, the instructing output of the delay circuit DL is supplied to the correction judging circuit CC. The output of the binary full adder FA is supplied through the delay circuit DL to the input side of the binary full adder FA as a binary carry signal and to the correction judging circuit CC as a decimal carry signal. The output of the correction judging circuit CC operates the generator CG. The output 0110 of the generator CG is supplied to the input side of the binary full adder FA In this way, 0-5 is transmitted as the output of the binary-coded decimal full adder AD, namely, that of the binary full adder FA,.

Although, in the embodiment, the carry detecting memory circuit DM has the memory capacity of four bits, it is a matter of course that the invention is not restricted thereto, but that three bits, for example, may

also be employed. In this case, a delay circuit for 1-bit delay is incorporated into an output supply line of, for example, from the correction judging circuit CC to the binary full adder FA, in FIG. 4.

A case where multiplication is carried out with the processing system of the present invention, will now be explained with reference to FIG. 5. FIG. 5 illustrates changes with time in information stored in the display register R in a calculating process in the case of executing the multiplication of 5 X 3 15.

First, the contents of all the shift registers are cleared to 0 beforehand. Next, when the multiplicand 5 is set by means of a number setting keyjik not shown) of the calculator, it is inputted from an input terminal i (FIG. 1) into and stored in the circulative memory circuit which the shift register R the correcting memory cir cuit DM and the feedback line FL, constitute. Subsequently, a function keylzlis depressed, and the multiplier 3 is set by a number setting keyE]. Then, the multiplicand 5 is transferred from the register R through the line FL, to the register Ry, and is circulated and held by the feedback path FL On the other hand, the multiplier 3 is stored, as in the foregoing setting of the multiplicand 5, in the circulative memory circuit constituted of the shift register R the correcting memory circuit DM and the feedback path FL.,. The circulative memory circuit stores therein the first or second operand corresponding to eight digits. The remaining eight digits are held in the blank 0 state.

Next, a calculation starting key (Elkey) is depressed, to initiate the calculation. Then, the multiplicand 5 set in the calculating register Ry is added to the information of the second display register R through the adder AD three times. The addition is carried out in the period of time in which the timing pulse Sp shown in FIG. 2b is at T FIG. 5b illustrates the state in which, after the first addition, an added result 5 is set in the display register R When the first addition is thus executed, l is subtracted from the multiplier 3 in R and the information of R at LSD becomes 31=2. The subtraction for R is carried out by the information Dt (refer to FIG. 1) for subtracting 1 as is generated in the period of time T of the timing pulse shown in FIG. 2b, and through the adder AD. Thereafter, the multiplicand 5 in Ry is successively added to the information in R in the same way, until the information at LSD of R becomes 0. The situations are illustrated in FIGS. 50 and 5d. When the information of R becomes 0, the calculation is stopped. The calculated result 15 is shifted rightwards from R to R and is set as in FIG. 5e. Thus, the multiplication is performed. In the case where the multiplier has many digits (at most eight digits), 1 is successively subtracted from the least significant digit to the most significant digit. In this case, the subtraction at each digit of the multiplier is carried out at LSD of R By way of example, consider the case of the multiplication of 5 X 13 65. In a state in which the additions for 3 at the first digit of the multiplier 13 have been completed (refer to FIG. 5d), the whole information in R is shifted rightwards, and is set as in FIG. 6a. Thereafter, the addition for l at the second digit of the multiplier is conducted as shown in FIG. 6b. In this manner, the calculation is performed while the information of the multiplicand at the respective digits in R are successively shifted rightwards to the least significant digit LSD of R Upon completion of the calculation, the answer is set with the standard at LSD of R as illustrated in FIG. 60. With such measure, if the calculated result exceeds the most significant digit MSD of R part of the information of the calculated result can be also set in R and hence, overflow is prevented. In the state before initiation of the calculation, it has been assumed that the second operand is stored in the circulative memory circuit of the register R while the first operand is stored in the register Ry. The calculation, however, may also be carried out with the positions of the first and second operands exchanged.

In case of performing division, processing is as below. By way of example, consider the case where the division of 4 2 2 is executed. As in the foregoing case of the multiplication, in a state in which number setting keys and a function key have been depressed, the first operand 4 is stored in the register Ry, while the second operand 2 is stored in the circulative memory circuit including the register R Next, the calculation starting key (ElKey) is depressed. Then, a shift instruction is first issued, so that the second operand 2 is shifted from the register R through the line F L to the register Ry and is stored therein, while the first operand 4 is shifted from the register Ry through the line FL, to the circulative memory circuit composed of the register R adder AD and feedback line FL, and is storedtherein (FIG. 7a). When a calculation starting instruction is subsequently issued to initiate the calculation, the dividend 4 is transferred to the least significant digit LSD of R as illustrated in FIG. 7b. The divisor 2 is successively subtracted from the information of LSD of R FIG. 70 shows a state in which the subtraction has been conducted once, and in which an information (calculated result) I indicating the one subtraction is set (added) at LSD of R In this manner, the subtractions are executed between R and Ry until the information of R becomes 0. In consequence, the answer 2 of the division can be obtained at LSD of R as shown in FIG. 7d. In this case, the addition of l to the information of R is effected from the input Dt, shown in FIG. 1. In the foregoing embodiments, the eight-digit register Ry is prepared for eight-digit numerical information. However, such modification is possible that, in order to prevent overflow of an integral part or to discriminate the sign of a number, one more digit is added to make the memory capacity of the register Ry 9 digits, that the memory capacity of the circulative memory circuit including the register R is accordingly made 18 digits, and that a digit signal Dt is added to those Dt, Dt

As described above, according to the present invention, the delay type full adder for binary-coded decimal signals is adopted. It forms the loop-like closed circuit jointly with the display shift register having a capacity integral times as large as that of the calculating shift register, and conducts additions in the series synchronism system. Therefore, the system of the invention makes it unnecessary to employ a number of controlling gates between shift registers, as compared with a prior-art system shown in FIG. 8 in which the shift registers of equal capacities are arrayed in parallel. Further, the use of the delay type binary-coded decimal adder makes it possible to constitute of a single line the line of the loop-like closed circuit which is formed by the display register R the delay type adder AD, a line a and the line FL A line b for the connection between the calculating register Ry and the adder AD can also be constituted of a single line.

Consequently, in accordance with the present invention, the number of controlling gate circuits to be connected anteriorly and posteriorly to each shift register can be made small. The correction memory circuit DM for correcting a pure binary number to a binary-coded decimal number, and the circulating register for display can be combined into one unit. Therefore, the circuit arrangement can be made simple. In case of bringing the construction according to the present invention into the form of an integrated semi-conductor circuit, the above feature is very advantageous in the degree of integration and the arrangement of the respective elements. In addition, in conformity with the present invention, the display register forms, along with the delay type adder, the loop-like closed circuit. Therefore, a predetermined position of the display register can be easily selected and controlled by the sector pulse. Processed information signals from the adder AD (information signals for display) can be successively set from the least significant digit of the lower digit portion one of the series-connected display shift registers. Therefore, the memory capacity for the display information signal can be made equal to the total capacity of the loop-like closed circuit. For example, in the case of the embodiment, a calculated result of at most 16 digits can be stored. In this case, when the number of digits of the indicating unit is eight, it is also allowed to control the lines FL and FL in FIG. 1 by making use of the foregoing sector pulses Sp, so as to display the higher eight digits or the lower eight digits. Overflow due to multiplication processing etc. can be prevented in this way.

Moreover, in conformity with the present invention, a calculated result to be displayed is circularly held by the loop-like closed circuit which includes the display register and the delay type adder. Therefore, it is not necessary to provide any special feedback path for the display register, and the dynamic display system can be easily adopted for the indicator unit (IN). More specifically, information is transmitted from the LSD part of the higher-digit display register R or that of the lowerdigit display register R to the indicator in FIG. 1 every digit by means of a gate controlled by every fourbit time. Thus, dynamic display signals can be easily taken out.

In this manner, with the digital processing system according to the present invention, calculating processing such as multiplication and division can be easily executed in the simple construction and using the binarycoded decimal numbers. In accordance with the inven tion, the circulative register can have the length shortened in its joint use for the memory circuit for the binary-coded decimal number correction. In addition, overflow can be aliminated with the resultant various advantages.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It should therefore be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. A digital processing system comprising a binarycoded decimal full adder having two binary full adders and a correction detecting memory circuit arranged therebetween and serving to subject two information inputs to addition and subtraction, the correction de tection memory circuit having a memory capacity, a first shift register having a fixed memory capacity and having an output connected to an input of said binarycoded decimal full adder, a second shift register having a memory capacity and having an output connected to another input of said binary-coded decimal full adder, means for connecting an output of said binary-coded decimal full adder with an input of said second shift register so as to form a loop-like circuit of said second shift register and said binary-coded decimal full adder, the total memory capacity of said second shift register and said detecting memory circuit being n times as large as said memory capacity of said first shift register where n is an integer of at least 2', and means for actuating the binary-coded decimal full adder to define a plurality of predetermined positions of said second shift register, information signals at said predetermined positions of said second shift register and in said first shift register being subjected to calculating and processing by said binary-coded decimal full adder, and a calculated and processed information signal being circularly held in said loop-like circuit.

2. A digital processing system according to claim 1, wherein said correction detection memory circuit means includes first, second and third delay circuit means, correction judging circuit means, generator means, said first full adder having an output connected to said first delay circuit means and another output connected to said second delay circuit means and to said correction judging circuit means, said second delay circuit means having an output connected to a third input of said first full adder which receives an output from said first shift register and an output from said calculating shift register means, said first delay circuit means having an output connected to a first input of said second full adder and an output connected to said correction judging circuit means, said correction judging circuit means having an output connected to the third input of said first full adder and an output connected to said generator means, said generator means having an output connected to a second input of said second full adder, said second full adder having an output connected to said second shift register and an output connected to an input of a gate circuit means, said gate circuit means adapted to receive a predetermined timing signal at another input thereof and having an output connected to said third delay circuit means, said third delay circuit means having an output connected to a third input of said second full adder.

3. A digital processing system comprising binarycoded decimal full adder means for subjecting two information inputs to at least one of addition and subtraction, said full adder means including circuit memory means having a fixed memory capacity, display shift register means providing an output to one input of said full adder means and including first and second series connected shift registers each having a memory capacity, and calculating shift register means having a predetermined memory capacity, said calculating shift register means receiving the output of said display shift register means at an input thereof and providing an output to another input of said full adder means, the output of the full adder means being applied to an input of the second shift register and the output of the first shift register being applied to the one input of said full adder means so as to form a loop-like circuit for circulation of information signals through the full adder means and the display shift register, the total memory capacity of said circuit memory means of said full adder means and said display shift register means being n times as large as the memory capacity of said calculating shift register means, where n is any integer greater than 1.

4. A digital processing system according to claim 3, wherein the memory capacity of the first display shift register is equal to the memory capacity of the calculating shift register means, and the memory capacity of the second display shift register is equal to the memory capacity of the first display shift register minus the memory capacity of the circuit memory means of said full adder means.

5. A digital processing system according to claim 3, wherein said binary-coded decimal full adder means includes first and second binary full adders and correction detection memory circuit means connected therebetween, said correction detection memory circuit means including said circuit memory means.

6. A digital processing system according to claim 5, further comprising display means for displaying the contents of said display shift register means.

7. A digital processing system comprising binarycoded decimal full adder means for subjecting two information inputs to at least one of addition and subtraction, said binary-coded decimal full adder means including first and second binary full adders and correction detection memory circuit means connected there between; display shift register means providing an output to one input of said full adder means, said display shift register means including first and second series connected shift registers; and calculating shift register means having a predetermined memory capacity, said calculating shift register means receiving the output of said display shift register means at an input thereof and providing an output to another input of said full adder means; the output of the full adder means being applied to an input of the second shift register and the output of the first shift register being applied to the one input of said full adder means so as to form a loop-like circuit for circulation of information signals through the full adder means and the display shift register; said correction detection memory circuit means including first, second and third delay circuit means, correction judging circuit means, and generator means, said first full adder having an output connected to said first delay circuit means and another output connected to said second delay circuit means and to said correction judging circuit means, said second delay circuit means having an output connected to a third input of said first full adder, said first full adder also receiving an output from said first shift register and an output from said calculating shift register, said first delay circuit means having an output connected to said second full adder and an output connected to said correction judging circuit means, said second full adder having an output connected to said second display register and another output connected to said third delay circuit means, said third delay circuit means having an output connected to an input of said second full adder and to an input of said correction judging circuit means, said correction judging circuit means having an output connected to- 8. A digital processing system comprising binarycoded decimal full adder means for subjecting two information inputs to at least one of addition and subtraction, said full adder means having circuit memory means having a memory capacity, display shift register means including a first and a second shift register connected in series and having memory capacities, respec tively, calculating shift register means having a memory capacity, first means for supplying an output of said first shift register to an input of said full adder means, second means for supplying an output of said full adder means to an input of said second shift register, third means for supplying an output of said calculating shift tegers of at least one, and N N 

1. A digital processing system comprising a binary-coded decimal full adder having two binary full adders and a correction detecting memory circuit arranged therebetween and serving to subject two information inputs to addition and subtraction, the correction detection memory circuit having a memory capacity, a first shift register having a fixed memory capacity and having an output connected to an input of said binary-coded decimal full adder, a second shift register having a memory capacity and having an output connected to another input of said binary-coded decimal full adder, means for connecting an output of said binary-coded decimal full adder with an input of said second shift register so as to form a loop-like circuit of said second shift register and said binary-coded decimal full adder, the total memory capacity of said second shift register and said detecting memory circuit being n times as large as said memory capacity of said first shift register where n is an integer of at least 2, and means for actuating the binary-coded decimal full adder to define a plurality of predetermined positions of said second shift register, information signals at said predetermined positions of said second shift register and in said first shift register being subjected to calculating and processing by said binary-coded decimal full adder, and a calculated and processed information signal being circularly held in said loop-like circuit.
 2. A digital processing system according to claim 1, wherein said correction detection memory circuit means includes first, second and third delay circuit means, correction judging circuit means, generator means, said first full adder having an output connected to said first delay circuit means and another output connected to said second delay circuit means and to said correction judging circuit means, said second delay circuit means having an output connected to a third input of said first full adder which receives an output from said first shift register and an output from said calculating shift register means, said first delay circuit means having an output connected to a first input of said second full adder and an output connected to said correction judging circuit means, said correction judging circuit means having an output connected to the third input of said first full adder and an output connected to said generator means, said generator means having an output connected to a second input of said second full adder, said second full adder having an output connected to said second shift register and an output connected to an input of a gate circuit means, said gate circuit means adapted to receive a predetermined timing signal at another input thereof and having an output connected to said third delay circuit means, said third delay circuit means having an output connected to a third input of said second full adder.
 3. A digital processing system comprising binary-coded decimal full adder means for subjecting two information inputs to at least one of addition and subtraction, said full adder means including circuit memory means having a fixed memory capacity, display shift register means providing an output to one input of said full adder means and including first and second series connected shift registers each having a memory capacity, and calculating shift register means having a predetermined memory capacity, said calculating shift register means receiving the output of said display shift register means at an input thereof and providing an output to another input of said full adder means, the output of the full adder means being applied to an input of the second shift register and the output of the first shift register bEing applied to the one input of said full adder means so as to form a loop-like circuit for circulation of information signals through the full adder means and the display shift register, the total memory capacity of said circuit memory means of said full adder means and said display shift register means being n times as large as the memory capacity of said calculating shift register means, where n is any integer greater than
 1. 4. A digital processing system according to claim 3, wherein the memory capacity of the first display shift register is equal to the memory capacity of the calculating shift register means, and the memory capacity of the second display shift register is equal to the memory capacity of the first display shift register minus the memory capacity of the circuit memory means of said full adder means.
 5. A digital processing system according to claim 3, wherein said binary-coded decimal full adder means includes first and second binary full adders and correction detection memory circuit means connected therebetween, said correction detection memory circuit means including said circuit memory means.
 6. A digital processing system according to claim 5, further comprising display means for displaying the contents of said display shift register means.
 7. A digital processing system comprising binary-coded decimal full adder means for subjecting two information inputs to at least one of addition and subtraction, said binary-coded decimal full adder means including first and second binary full adders and correction detection memory circuit means connected therebetween; display shift register means providing an output to one input of said full adder means, said display shift register means including first and second series connected shift registers; and calculating shift register means having a predetermined memory capacity, said calculating shift register means receiving the output of said display shift register means at an input thereof and providing an output to another input of said full adder means; the output of the full adder means being applied to an input of the second shift register and the output of the first shift register being applied to the one input of said full adder means so as to form a loop-like circuit for circulation of information signals through the full adder means and the display shift register; said correction detection memory circuit means including first, second and third delay circuit means, correction judging circuit means, and generator means, said first full adder having an output connected to said first delay circuit means and another output connected to said second delay circuit means and to said correction judging circuit means, said second delay circuit means having an output connected to a third input of said first full adder, said first full adder also receiving an output from said first shift register and an output from said calculating shift register, said first delay circuit means having an output connected to said second full adder and an output connected to said correction judging circuit means, said second full adder having an output connected to said second display register and another output connected to said third delay circuit means, said third delay circuit means having an output connected to an input of said second full adder and to an input of said correction judging circuit means, said correction judging circuit means having an output connected to said generator means, and said generator means having an output connected to another input of said second full adder.
 8. A digital processing system comprising binary-coded decimal full adder means for subjecting two information inputs to at least one of addition and subtraction, said full adder means having circuit memory means having a memory capacity, display shift register means including a first and a second shift register connected in series and having memory capacities, respectively, calculating shift register means having a memory capacity, first mEans for supplying an output of said first shift register to an input of said full adder means, second means for supplying an output of said full adder means to an input of said second shift register, third means for supplying an output of said calculating shift register to another input of said full adder means, and fourth means for supplying an output of said first shift register to an input of said calculating shift register and bypassing said full adder means.
 9. A system according to claim 8, wherein the memory capacity of said circuit memory means of said full adder means is 4 N1 bits, the memory capacities of said first shift register and said calculating shift register are both 4N2 bits and the memory capacity of said second shift register is 4(N2-N1) bits, where N1 and N2 are integers of at least one, and N2 > N1. 